Solenoid controlled pressure regulating and shut-off valves (PRSOV) are designed to operate in the inlet anti-ice system of an aircraft engine. A known PRSOV comprises two pistons within sleeves defined by the main body of the valve. The shut-off function is pneumatically operated and electrically controlled by an on-board mounted solenoid valve, while the pressure regulating function is controlled by a pressure relief valve. Both functions are achieved using the inlet pressure and flow as power muscle to the control elements. In order to enable the operations of the control elements, suitable passages are machined within, or externally affixed to, the valve, for example as pipes. A manual override is often included which enables operation and locking of the valve in the fully open position.
The PRSOV is a compact unit which may provide multiple functions. For example, the PRSOV may provide a regulating function for regulating downstream engine bleed air pressures, which is activated when the solenoid is de-energized. The PRSOV may also provide a shut-off function for stopping downstream engine bleed air, which is activated when the solenoid is energized. The PRSOV may also be provided with a mechanism for manually overriding the regulating and/or shut-off functions, for example by locking the PRSOV in an open or a closed position.
A conventional pressure regulating shut-off valve 10 is shown in FIG. 1. The valve comprises an inlet 16, an outlet 13, a pressure relief valve 12, a solenoid valve 11, and a duct 14. Duct 14 is installed on the valve to allow fluid communication between the valve inlet 16 and the solenoid valve 11 for controlling the shut-off function. The solenoid may control the flow from the duct 14 to actuate a shut-off cylinder within the valve to prevent airflow from the inlet 16 to the outlet 13.
PRSOVs must operate in extreme temperature and pressure conditions, and must be reliable enough to ensure flight safety. The materials that PRSOVs are made of must therefore be able to accommodate high temperatures and pressures, while being sufficiently durable to be ensure safely. It is also desirable that PRSOVs should be as light as possible, since they are employed in aircraft.